An administrator is reviewing DNS lookup behaviors and transport protocol characteristics for enterprise host name resolution. Which two statements correctly describe DNS operations and protocol roles during name resolution? (Choose two.)
- Standard client DNS query requests and small responses typically use UDP port 53 to reduce latency and header overhead.Answer
- BAn iterative DNS query requires the queried DNS server to fully resolve the domain name on behalf of the client by contacting other authoritative servers.
- DNS switches to TCP port 53 when a response payload exceeds the standard buffer limit or during zone transfers between DNS servers.Answer
- DDNS queries use UDP port 53 because UDP inherently guarantees packet sequencing and automatic retransmission of lost queries.
- EClient workstations perform DNS reverse lookups using MX records to convert IPv4 addresses into Fully Qualified Domain Names (FQDNs).
Answer
Standard client DNS queries primarily use UDP port 53 to minimize transport overhead, but DNS fallback to TCP port 53 occurs when response sizes exceed buffer limits or during server-to-server zone transfers.
DNS queries use UDP port 53 by default because connectionless transport reduces overhead and latency for simple lookups. When response data exceeds standard message length thresholds or during DNS zone transfers between servers, DNS relies on TCP port 53 for reliable connection-oriented delivery.
Step-by-Step Solution
Key Concept
DNS Transport Protocols and Server Resolution Roles